Governments and industrial concerns on a priority basis are dedicating increased attention to alternatives to petroleum as sources for fuels and chemical intermediates, i.e., coal and wood. Substantial reserves of coal exist in highly industrialized countries, and wood is both plentiful and replenishable worldwide.
Since most current energy utilization technology requires liquid energy media, it has become an important research and development objective to provide innovative means to convert coal into liquid sources of potential energy.
It was recognized by early workers that coal can be liquified by controlled heating in the substantial absence of oxygen. The conversion products are a liquid and a char. Because of the new compelling economic factors, the technology of coal liquefaction and gasification has been expanding at an accelerated pace. Pioneer developments in the field are represented by Lurgi and Fischer-Tropsch technology. More recent advances in coal liquefaction are described in U.S. Pat. Nos. 1,904,586; 1,955,041; 1,996,009; 2,091,354; 2,174,184; 2,714,086; 3,375,188; 3,379,638; 3,607,718; 3,640,816; 3,642,608; 3,705,092; 3,849,287; 3,870,621; inter alia.
The primary product of such coal liquefaction processes is a mixture of liquid and undissolved solids. The liquid is a solution of coal solubilization products dissolved in the liquefaction solvent. Most of the undissolved solids may be readily separated from the liquid by conventional solids-liquid separation processes such as filtration, centrifugation, sedimentation, hydroclones, and the like.
The prior art provides various methods for the separation of coal liquefaction liquids from undissolved solids. Illustrative of the prior art pertinent to such solids-liquids separation methods are U.S. Pat. Nos. 2,060,447; 2,631,982; 2,774,716; 2,871,181; 2,964,460; 2,989,458; 3,010,893; 3,018,241; 3,275,546; 3,519,553; 3,598,118; 3,607,716; 3,607,717; 3,607,718; 3,607,719; 3,635,814; 3,642,608; 3,687,837; 3,791,956; and Def. Publ. 700,485. One of the objectives of the prior art processes is maximum recovery of a coal liquefaction product which is substantially free of mineral matter. Other objectives include sulfur and oxygen removal.
The prior art provides various methods for upgrading coal liquefaction products. Conversion of solvent refined coal liquids into high grade motor fuels can be achieved by catalytic cracking and hydrocracking processes. Catalytic conversion of coal liquids has been hampered by the presence of nitrogen-containing organic derivatives in the coal liquids. Denitrification by catalytic means requires severe operating conditions, which results in high hydrogen consumption and a concomitant reduction of aromatic compounds.
There remains a pressing need for new technology for the conversion of coal into high value liquid carbonaceous products to complement and to enhance conventional petroleum derived energy applications. Further, there is a need for liquified coal products which qualify as premium gasolines which are high octane.
Accordingly, it is a main object of this invention to provide an improved method for converting solid carbonaceous materials into liquid derivatives having application as fuels.
It is another object of this invention to convert coal into a denitrified synthetic crude oil.
it is a further object of this invention to solubilize coal and upgrade the resultant liquid product for application as premium gasoline stock.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.